1. Field of the Invention
The present invention relates to a strain of measles virus vaccine comprising a specific nucleotide sequence, and a method for its absolute identification.
2. Description of the Prior Art
Measles virus is the causative virus of measles, and belongs to the Paramyxoviridae family of RNA virus.
The first isolation of measles virus from patients using a primary culture of human kidney cells was made by J. F. Enders et al. in 1954 (Enders, J. F. et al., Proc. Soc. Exp. Biol. Med., Vol. 86, pp. 227-286, 1954). Attenuated measles virus vaccine was developed using the isolated Edmonston strain by Enders et al. (Enders, J. F. et al., New England J. Med., Vol. 263, pp. 153-259, 1960). However, the vaccine developed by Enders et al. frequently induced adverse effects including pyrogenicity and exanthema.
Many strains of attenuated measles virus having been established by further attenuation of the Edmonston strain. Among these strains the Schwarz strain established by A. J. F. Schwarz has been commonly used for live measles vaccines.
The present inventors have isolated four strains of a cold variant derived from attenuated measles virus of the Edmonston strain, supplied by Dr. Enders (Makino, S. et al., Jap. J. Microbiol., Vol 14, pp. 501-504, 1970).
Reduction of immunogenicity, i.e. effectiveness, according to a development of attenuation of measles virus has generally been known. Among the strains of the isolated cold variant, a viral strain which grows adaptively at 33.degree. C. was found to be a further attenuated measles virus with high immunogenicity having properties different from those generally observed in the conventional measles virus (Makino, S. et al., Jap. J. Microbiol., Vol. 17, pp. 75-79, 1973).
In order to develop the seeds for live measles vaccines from the cold variant, one of the present inventors has isolated clone virus which is a strain adapted with chick embryo cells obtained from specific pathogen-free eggs, having the same temperature marker, and designated as the AIK-C strain (Sasaki K., Kitasato Arch. Exp. Med., Vol. 47, pp. 1-12, 1974).
The pyrogenicity ratio (.ltoreq.37.5.degree. C.) of an AIK-C strain live vaccine produced from the seeds of AIK-C strain in measles-sensitive infants approximately 1/3-1/4 as compared with that of Schwarz strain vaccine. The AIK-C strain has been found to be a further attenuated measles virus than the Schwarz strain, with the unique characteristic of having a high immunogenicity response without lowering immunogenicity (Makino, S. et al., Kitasato Arch. Exp. Med., Vol. 47, pp. 13-21, 1974).
Encephalitis that seems to be caused by administered live measles vaccine has been observed in 1-3 persons per million treated infants. However, this neurological complication has never been reported in the case of the AIK-C strain in spite of the administration of AIK-C strain live measles vaccine to ten million people in Japan (Hirayama, M. et al., Inf. Dis., Vol. 5, pp. 495-503, 1983; Makino, S., Vol. 5, pp. 504-505, 1983).